Getting back into HF again

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Getting back into HF again

Postby 2E0LDQ » Thu Mar 17, 2016 7:00 pm

Hi,
So it's been about a year since I last had a HF radio in my house,
I am wanting to get another and get back into HF,
But I'm afraid that the problems I suffered from before, that caused me to give up and sell the HF gear, will return and I will be in the same situation,
Last time I had a Yaesu FT-450D, connected to a G5-RV,
But I was getting nothing but problems and it was really upsetting me as I couldn't get to the bottom of it at all,
Basically, everytime I was to use the radio and key up on my licenced power of 50w or even below on lowest power,
Everything in the house would literally go crazy, the landline phones would ring and both of my games consoles etc.. Would eject discs everytime I keyed the mic,
Even my Yaesu ft400dr would go crazy, the screen would pixelate and judder, then the whole thing would cut out and shut off,
I had ferrite fitted to everything it was affecting and even the coax coming into the room,
I just couldn't get to the bottom of the problems it was causing me, so I had to sell the gear and stick to 2m,
As mentioned above, I would really like to get back into HF and have my eye on a radio,
But with the problems I had before, I just can't buy another Incase these problems arise again,
Has anybody experienced this or similar, or could kindly offer me any advice at all on what you think could be causing the issues,
I am looking to buy a Yaesu ft-950 and don't want this to happen again, as I would be really upset,
Very much appreciated in advance, and thanks,
Liam.
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Re: Getting back into HF again

Postby m0lsx » Thu Mar 17, 2016 10:36 pm

Sounds like you potentially had common mode current coming back into the shack..Did you use a balun at the G5RV feed point & did you try a clip on ferrite with the coax looped through it before the coax entered the shack &/or just before the radio??
A ferrite clip on or two will not stop common mode current as you need a lot of impedance to stop common mode of the longer wavelengths, but a few loops of coax through a ferrite will do it.

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Re: Getting back into HF again

Postby 2E0LDQ » Thu Mar 17, 2016 11:23 pm

I had the G5-RV as I bought it, I assembled it out of the box and connected coax to the end of the ladder feeder,
Then fed it straight into my room and Into the radio,
I used 1 little ferrite clamp on the coax before it entered the radio antenna socket right before the 259 plug,
That was it,
I didn't have any ferrite rings or ferrite clamp ons, on the coax outside,
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Re: Getting back into HF again

Postby m0lsx » Fri Mar 18, 2016 12:04 am

You need more than that.. It is normal to have an isolation (1:1) balun at the feed point of the antenna & if you are getting a common mode issue, then keep it out of the shack altogether by putting a couple of loops through a ferrite before it enters the shack.
Also have a look at the ZS6BKW it's like a G5RV, but actually resonant away from 20 meters, more efficient & less likely you give issues. But it still needs that 1:1.

http://www.ab4oj.com/dl/sprat_zs6bkw.pdf

http://ars.nc4fb.org/zs6bkw/zs6bkw-antenna-from-the-horses-mouth-by-g0gsf.pdf

https://vk4mdx.wordpress.com/2013/09/02/how-to-build-a-zs6bkw-antenna-optimised-g5rv-antenna/
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Re: Getting back into HF again

Postby 2E0LDQ » Fri Mar 18, 2016 9:50 am

Thanks for the replies,
So getting a few of the big round ferrite rings,
And wrapping 9-10 loops of coax through it, inside before the radio and outside before it enters,
This should cure it ?
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Re: Getting back into HF again

Postby m0lsx » Fri Mar 18, 2016 11:20 am

Ideally you do not want that Common mode on the coax at all, so put a choke (1:1 or a series of beads over the coax,) at the feed point. & then what I do is I put a second choke just before the coax enters the building. For me that second choke serves a dual purpose, it takes water off the coax too.
I also like Baluns because they provide an electrical break between the antenna & the radio & that helps a little with some QRM.
The other issue is what earthing do you use for your radio??
Here my radio is on the first floor so I have to use an artificial earth. But every little helps.
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Re: Getting back into HF again

Postby G4RMT » Fri Mar 18, 2016 6:20 pm

I thought I replied to this - in fact, a huge post, but it vanished on the way.

What concerned me was that clearly here RF, even modest amounts of it are getting into the system somewhere, and we're talking about a cure, when something else is wrong.

Home wiring nowadays (certain in the UK) tend to have the live and neutral coming into the home with a ground, and then this ground is connected to neutral at the point where the distribution to the various circuits takes place. Having earth stakes and rods bashed into the ground also are common, especially so when power is supplied from overhead cables from the local pole.

In this case, I'm wondering of the real issue is that the safety ground is actually poor, or even missing? Everything would work fine, but all the grounds in the home could be acting like a big aerial system, floating at a totally different potential to the house ground. If your aerial is grounded, or there is a decent proper ground somewhere, if you have the equipment, it would be sensible to meter the real ground to the house electrical ground. Normally you'd expect a few volts, especially if the distance from the main ground to some outlets is large, but anything much more than a few volts might mean your ground is faulty/missing.

Before you spend time and effort sorting out the RF issue, I'd check the safety aspects, as the ground is there to protect the users.

Clearly there is something odd going on here - and loss of the safety ground could be the open door to RF?
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Re: Getting back into HF again

Postby 2E0LDQ » Fri Mar 18, 2016 7:05 pm

Thanks to all who have replied,
G4RMT, I am still all new to the world of amateur radio, so I am not all that technically minded yet,
Although I am studying for my advanced licence,
Anyway,
You mention grounding and earthing, will this mean the ground and earth for the home electricity supply ?
As there is numerous earth wires coming from the house wall going into a device down in the driveway,
I only know they're earth wires as they're shielded green and says earth, I hope so anyway,
I have been advised to try a 12v car battery, which I do have a spare one in the garage that I could try I suppose,
But this won't really cure the problem, I can't be running from a car battery for the rest of its life,
I haven't purchased another radio yet, but I don't want to be shelling out £700 on a Yaesu ft-950, if I'm going to have the exact same problems as before,
M0lsx mentioned artificial earthing, without sounding stupid, how would I go about this, and would that cure the issues ?,
I really do appreciate all of the people taking the time to reply to my post,
It's only for this reason that's stopping me going out right now and buying another HF radio,
Once again thanks for the help, I'm sure we will get to the bottom of it.
Liam.
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Re: Getting back into HF again

Postby G4RMT » Fri Mar 18, 2016 7:48 pm

The thing here is that in normal circumstances RF problems like this are caused by the RF from the aerial system getting back int the electronics of your own radio kit and your TV, radio, hifi, plus of course even odder equipment like burglar alarms.

Earth, as we call the US ground is designed as a kind of conductor - In theory, ground, is a low resistance current path, and in RF theory it becomes a kind of counterweight for the RF being launched into the ether. A car roof is metal and a modest ground plane (or counterpoise - an alternative name, but not one I use). A biscuit tin isn't. Too small. Some aerials use ground plane rods, which 'blend' together to become an effective ground plane. HF wise, with a vertical, the earth itself becomes the 'ground' but loose dry sandy soil is less good than good old english mud - which being wetter and full of acidity tends to be better. In commercial radio sites it's common to bury copper wire under the surface to make it even better. If your home is not grounded properly, then all those earth wires are not connected to the proper grounding system. In effect, it's an aerial capable of receiving what you squirt out, and it's connected to much of your electronics!

The idea of a 12V system simply isolates your radio system from cables, just in case the RF was creeping in down the supply cable. All the ferrite devices mentioned just load the supply cables so they are a low impedance to RF, pretty close to a short - which stops the RF passing down the cable, while letting the supply voltage pass. These gizmos are fitted to so much kit nowadays like power supplies - stopping the noise their switch mode supplies produce.

In the example here, even low power levels cause it to be unstable. Attempts to block it have failed, so something odd is happening. If it is a real fault then interference is the smallest problem - any fault condition that would normally shunt the plains down to earth and blow a fuse or trip a breaker won't work, and worse still, metal cases could become live.

In my live sound and theatre world where I work, hum is always a problem and some idiots disconnect the earth wire. Cures the hum, but a dodgy guitar amplifier can make the metalwork live at about half the mains voltage - so your guitar strings can be metered at 110V. Touch a microphone with your lips, and because that is connected to the real ground, the 110V tries to become 0V by going through your lips! Possibly terminal, but very unpleasant. Ham gear tends to be pretty reliable, but faults still do happen.

Doing a voltage test between two earth connections should produce zero. In my house, I can get about 4 Volts difference at my garden shed - because of the long cables. More than that, and I'd start to be concerned.
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